It's a spurious "\??mathstylecache" in math-ini.mkiv and I sent a fix to the dev-list.21. Dezember 2015 um 14:14Hi Dalyoung,
I can confirm that in displayed math, the digit 1 in the command \frac{1}{2} results in
494 > 1
which is unexpected…
However the command {1 \over 2} gives the correct result.
Actually there seems to be a spurious
494 >
in the source tree of the latest release, since any command such as \frac{a}{2} results in
494 > a